There is a clutch control device known in the related art that, after the displacement of one hydraulic motor becomes zero, disengages the clutch connected to the hydraulic motor and uses only the output of the other hydraulic motor so as to drive the vehicle (refer to, for example, patent reference literature 1). The device disclosed in Patent Reference Literature #1 disengages the clutch when the vehicle speed becomes greater than or equal to a predetermined value after the displacement of the hydraulic motor becomes zero.    Patent Reference Literature 1: Japanese Laid Open Patent Publication No. H11-230333